1. Field
The present disclosure relates to a fuel cell, and more particularly, to a stack of for a fuel cell.
2. Discussion of the Related Technology
Generally, a fuel cell includes a generator for generating electrical energy by an oxidation reaction of fuel and a reduction reaction of an oxidizing gas. The fuel cell may be classified as a polymer electrolyte membrane fuel cell and a direct oxidation fuel cell according to a type of fuel. In the polymer electrolyte membrane fuel cell, a reformed gas from a liquid or gas fuel and an oxidizing gas are received, and electrical energy is generated by an oxidation reaction of the reformed gas and a reduction reaction of the oxidizing gas. In the direct oxidation fuel cell, liquid fuel and oxidizing gas are received, and electrical energy is generated by an oxidation reaction of the fuel and a reduction reaction of the oxidizing gas.
The fuel cell is formed as a stack in which unit cells respectively including a membrane electrode assembly (MEA) and a separator are sequentially arranged. Here, the separator is disposed on both sides of the membrane electrode assembly, and both sides respectively include a channel for supplying the reformed gas or fuel and the oxidizing gas to the membrane electrode assembly. In the above fuel cell, the separator of the unit cell is formed of composites containing graphite or carbon, and a thickness of the separator is not less than about 0.4-about 0.6 mm to prevent a gas or a liquid from penetrating the separator. Accordingly, there are problems of excessive thickness of the separator, a complicated manufacturing process, and a high cost. Recently, a metal separator has been used to solve the above problems. In this separator, there is a merit in that the thickness is reduced to be less than that of the graphite- or carbon-containing composites. In the metal separator, to maintain a minimum thickness, a stamping process is performed to form the channel at both surfaces of the separator. However, while corrugated channels having opened ends are formed on the entire plane surface of the separator, an additional manifold for supplying the reformed gas or fuel and the oxidizing gas to the channel is not formed. When the stack includes the separator without the manifold, a pumping pressure for supplying the reformed gas or fuel and the oxidizing gas to the channel is increased, and therefore power consumption of a pump is problematically increased.
In addition, a single serpentine channel may be formed on one surface of the separator by the stamping process to form the manifold to the separator, but the channel may not be formed on the other surface of the separator. Accordingly, according to the prior art, the serpentine channel is formed by the stamping process on one surface, and the respective separators include the manifold connected to the channel. However, in this case, it is difficult to minimize the volume of the entire stack.
The discussion in this section is to provide general background section, and does not constitute an admission of prior art.